The MicroScan WalkAway diagnostic microbiology system--an evaluation.

The MicroScan WalkAway is an automated bacterial identification and susceptibility testing system that has only recently been marketed in Australasia. We evaluated the performance of the instrument using MicroScan Rapid fluorescent panels to determine the identity and antibiotic susceptibilities of 100 Gram negative and 100 Gram positive organisms representing both common clinical isolates and selected organisms of interest. MicroScan results were compared with those obtained by conventional biochemical identification, and antibiotic susceptibility testing using agar dilution following the National Committee on Clinical Laboratory Standards guidelines. MicroScan and reference identifications were in agreement for 93% of Gram negative organisms. MicroScan results were available within 2 hrs. Additional tests were required to confirm the identity of 9 isolates but on only 2 occasions would a definitive identification been delayed beyond 24 hrs. Very major or major discrepancies were seen in 2% and minor discrepancies in 8% of Gram negative susceptibility tests. Susceptibility results were available within 7 hrs but could not be obtained for 13 slow growing organisms. With Gram positive organisms MicroScan agreed with the reference identification of 87% of isolates cultured on horse and 90% of those cultured on sheep blood agar. Discrepancies that occurred in the identification of some streptococci made us question the suitability of MicroScan as the sole means of identifying these organisms. All identifications were available within 24 hrs and the requirement for additional tests was minimal. Susceptibility results closely matched those obtained by agar dilution with < 1% major and 7% and 9% minor discrepancies occurring with sheep and horse blood respectively.(ABSTRACT TRUNCATED AT 250 WORDS)